Generally, a power inverter includes a smoothing capacitor module that receives DC power from a DC power source, an inverter circuit that receives DC power from the capacitor module and generates AC power, and a control circuit that is used for controlling the inverter circuit. The AC power, for example, is supplied to an electrical motor, and the electrical motor generates rotating torque in accordance with the supplied AC power. Generally, the electrical motor has a function of a generator, and, when mechanical energy is supplied to the electrical motor from the outside, the electrical motor generates AC power based on the supplied mechanical energy. In many cases, the above-described power inverter has a function for converting AC power into DC power, and the AC power generated by the electrical motor is converted into DC power. The conversion from DC power to AC power or the conversion from AC power to DC power is controlled by the control device. For example, when the electrical motor is a synchronous electrical motor, by controlling the phase of a rotating magnetic field generated by a stator with respect to a magnetic pole position of a rotor of the synchronous electrical motor, the control relating to the power conversion can be performed. An example of the power inverter is disclosed in PTL 1.
The power inverter, for example, is built in a vehicle, receives DC power from a secondary battery built in the vehicle and generates AC power to be supplied to an electrical motor generating rotating torque for driving. In addition, when the vehicle is in a regenerative braking operation, in order to generate a braking force, the electrical motor generates AC power based on drive energy, and the generated AC power is converted into DC power by the power inverter, which is charged in the secondary battery and is used again as power for driving the vehicle.